The University of Minnesota has been under contract to the National Cancer Institute in evaluating the health of nearly 145,000 workers certified by the American Registry of Radiologic Technologists since 1982. A comprehensive baseline survey was completed by more than 90,000 technologists between 1984-1989. A second survey is ongoing to obtain detailed information on cancers diagnosed since the first survey. The objectives of this contract are to complete and extend the survey of cancer incidence among U.S. x-ray technologists and to quantify the risk of specific cancers associated with occupational radiation exposures. Extensive application of biological dosimetry techniques will be used to characterize radiation exposures. In addition, the possible role that genetic susceptibility may play in radiation-induced cancers will be evaluated among women who developed breast cancer under the age of 35.